Recently, considerable effort is being expended to develop wings capable of generating tractive force for the purposes of powering a user on a variety of vehicles that are tethered solely by flexible lines. Such wings can generally be considered kites. The development of kites capable of generating significant force has made possible numerous recreational pursuits. For example, kite surfing or kite boarding refers to a sport involving the use of a wind powered wing to pull the participant on a vehicle across a body of water. Similar sports involving the use of appropriately configured vehicles to traverse sand, earth, snow and ice are also being pursued. One of skill in the art will also recognize that wind powered wings can be used in any number of other applications, whether recreational or practical. With the development of these applications has come an increasing demand for kites having improved characteristics.
One type of kite that has achieved popularity is a leading edge inflatable (“LEI”) kite, typically comprising a semi-rigid framework of inflatable struts or spars that support a canopy to form the profile of the wing. This basic design is taught by U.S. Pat. No. 4,708,078 to Legaignoux, et al. The development of the LEI kite is generally credited with spurring the development of modern kite surfing due to its ability to be relaunched from the water's surface.
Despite the success of LEI kite design, they do suffer from certain, inherent challenges. A significant consequence of the use of inflatable struts is difficulty in maintaining the stability of LEI kites in use. This is particularly true when the kites are used in gusty or turbulent conditions. If insufficient pressure is used to inflate the struts, an undesirable flexibility can be imparted to the framework. However, practical considerations limit the amount of pressure that can be used. Higher pressures require the use of more expensive materials and more exacting manufacturing tolerances. Such pressures also increase the possibility of puncture or rupture failures and more generally detract from the overall convenience of the design.
The various characteristics considered desirable for the practice of kiteboarding suggest a number of possible LEI kite design parameters. Some of these characteristics include efficiency, durability, economy of manufacture, relaunchability, performance, handling and power control, most of which are interrelated. For example, attempts to improve the performance of a kite often involve increasing the aspect ratio of the wing. However, the ability of the kite to be relaunched tends to be inversely related to the aspect ratio. Likewise, one aspect a kite's efficiency is its lift to drag ratio, but increasing this ratio can have adverse effects on the handling of the kite. As yet another example, the durability of a kite can be improved by using stronger materials, but usually with the drawbacks of increasing the weight of the kite (and thus decreasing performance) and cost of manufacture. All of these characteristics depend to some degree upon the stability of the canopy and the rigidity of the wing in flight.
Accordingly, it is an object of the present invention to provide a LEI kite design that offers improved canopy stability.
It is also an object of the present invention to provide a LEI kite design that exhibits greater framework rigidity.
It is another object of the present invention to provide a LEI kite design increases the stability of kite at relatively lower inflation pressures.
It is yet another object of the present invention to provide a LEI kite design that maintains performance while decreasing weight and increasing durability.
It is an also an object of the present invention to provide an aerodynamic wing having a canopy surface with controlled alteration of lifting characteristics in response to forces experienced by the wing. Specifically, the canopy surface comprises inflatable structures that extend the canopy